1. Field of the Invention
The invention relates to an aircraft jet engine.
2. Description of the Related Art
In known manner, an aircraft jet engine comes in the form of a nacelle in the center of which a turbomachine is positioned.
This nacelle is intended to be installed under the wing group of an aircraft by means of an engine nacelle pylon.
The turbomachine consists of a gas generator that drives a fan installed on the shaft of the gas generator, upstream from the latter along the longitudinal direction of the jet engine nacelle.
The air stream that passes longitudinally through the nacelle penetrates partially into the gas generator and takes part in combustion.
This stream is called primary stream and is ejected at the outlet of the generator.
The part of the air stream penetrating into the nacelle and that does not pass through the gas generator is carried along by the fan.
This stream, called secondary stream, flows in an annular passage, concentrically in relation to the primary stream. This passage is formed between an outer longitudinal wall (nacelle wall) and an inner longitudinal wall surrounding the gas generator.
The secondary stream is ejected from the nacelle at the downstream end of the outer wall of the latter along the more or less longitudinal direction of the jet engine.
The inner wall surrounding the generator for the gas also defines with an inner longitudinal part an annular passage through which the primary stream flows.
This stream is ejected at the downstream end of the inner wall that surrounds the gas generator.
During take-off phases, the gas stream that is ejected (primary and secondary stream) takes on very high speeds. At these speeds, the meeting of the ejected stream with the surrounding air, as does the meeting of the primary stream and the secondary stream, generates a considerable noise.
A fluidic device for reduction of noise generated by an aircraft jet engine is known from international application WO2002/013243.
This device comprises several pairs of ducts opening into the outlet of a nozzle of the jet engine that ejects a propulsive jet and which are distributed around the periphery of this nozzle.
The ducts of each pair each eject an air jet and are disposed in convergent manner in relation to each other in order to generate at the outlet a triangle of interaction of the air jets.
The angle of convergence of the ducts is between 40 and 70°.
This device is satisfactory for small nozzle sizes.
Nonetheless, when the diameters of the nozzles take on relatively high values, for example on the order of a meter, the aforementioned device loses its effectiveness.
The fluid jets originating from the convergent ducts in fact cannot interact with the entirety of the propulsive jet ejected by the nozzle. For this reason, a portion thereof meets the external peripheral flow of air, thus generating noise.
A need therefore exists to reduce the noise caused by the ejection of the gas stream or streams at the outlet of a jet engine nacelle of an aircraft, in particular when the dimensions of the jet engine are considerable.